The introduction of osteosynthesis material or implants for secure attachment of two bone fragments to one another—independently of whether they occurred as a result of a traumatic fracture or were caused iatrogenically by targeted intraoperative separation of a bone (osteotomy)—is a frequent task in accident surgery and orthopedics.
This task represents a special technical challenge for the operator. For example, in the not infrequently necessary surgical correction of incorrect positioning of bones, an iatrogenic separation of the bone with the removal of a correcting wedge is usually necessary. Depending on the procedure, in the case of many osteosynthesis implants (for example angle plate for the upper thigh bone near the hip joint), the anchoring of an implant must be prepared ahead of time before separation of the bone in the bone that will later be a fragment, using a bone blade chisel [Müller 1984, Burgkart 2005]. As long as the bone is intact and as a result of this can be worked on with a chisel and striking tools (the subsequent fragment would be too fragile), the proximal implant anchoring must already be prepared, whereby the operator can predict the later new positioning of the bone fragment complex formed first—previously only with the ability of his spatial imagination—and from that he has to derive the operative procedure.
In other words, in order to correct the faulty position, the bone must be sawed all the way through and be put together again. Before the joining together, a wedge-shaped piece must be removed by means of another saw cut. Then the two parts must be rejoined together while keeping the cut surfaces held together and pressed together, to the extent possible, over the entire surface. For this purpose an angle-shaped implant is used with a long and short lateral side. The short lateral side is hammered into the first bone section (joint head) and the long lateral side is screwed into the second bone section.
In order to be able to hammer the short lateral side into the first bone section, previously a hole with a specific depth, direction and cross-section must be prepared in the particular bone section, with a chisel.
However, in order to hammer in this hole, it is necessary that the bone not yet be separated, because otherwise the first bone section would deviate during the procedure with the chisel since it cannot be held in a fixed manner yet, but is only surrounded by muscle and fatty tissue, which does not provide any hold when the chisel is struck into the bone.
Thus, when viewing the now partly freed bone, the operator must imagine where and in what direction the hole is to be hammered in. For this purpose, the operator must develop a high degree of spatial imagination, so that the hole is produced in such a way that after the separation of the bone and the correction it is in the exactly correct location to be able to accept the implant in the correct position.
It is understandable that these circumstances frequently lead to sub-optimal implant positions, so that either an attempt is made to “compensate” for it by a slight correction—as planned and needed—and/or there is an increased risk of delayed bone healing and loosening of the implant and thus the necessity of repeated surgery(ies).
The exact performance of such an operation is very difficult technically and so far depended greatly—more so than in other procedures—on the experience and manual skill and ability of imagination of the operator. Therefore, there is an urgent need for a technique that simplifies these surgical steps, supports them, and allows them to be better planned.
The first modern approaches to solving this problem consist in the use of computer-assisted navigation methods. Hereby, as a rule, a navigation system (computer-assisted control unit connected to a navigation camera) is used, a reference unit that is attached to the patient as well as calibrated surgical tools. The reference unit and the surgical tools are hereby provided with active or passive markers and in this way can be detected with regard to their spatial position and direction by the navigation camera, whereby these data are then transmitted to the control unit. In this way tools that are moved by hand can be tracked and, when referenced imaged data are available, the tools can, for example, be virtually merged into the image data corresponding to their instantaneous position and thus help the operator during the procedure, and at the same time make various virtual plans possible, for example as described in U.S. Pat. No. 6,226,548 No. 6,747,646; No. 6,752,080 No. 6,697,664; No. 6,535,756; No. 6,470,207; No. 6,205,411; see also the literature references below, which are also included in the present application as state of the art.    Burgkart R, Doter M, Roth M, Schweikard A, Gradinger R: Fluoroscopy-based 3D-navigation at the proximal femur. In: Imhoff A (ed) Computer Assisted Orthopedic Surgery—Fortbildung Orthopädie 6. Steinkopff, Darmstadt 2002, pp. 39-43.    Burgkart R, Gottschling H, Roth M, Gradinger R, Schweikard A.: Fluoroscopy-based 3D navigation of complex corrective osteotomies on the proximal femur. Orthopäde. 2005 November; 34(11): 1137-43.    Foley, et al., Image-guided Intraoperative Spinal Localization, Intraoperative Neuroprotection: Monitoring, Part Three, 1996, pp. 325-340.    Gottschling, H., Roth, M., Schweikard, A., Burgkart, R.: Intraoperative, Fluoroscopy-based planning for complex osteotomies of the proximal femur. International Journal of Medical Robotics and Computer Assisted Surgery 2005 September; Vol. 1(3): 67-73.    Früitzner PA, Suhm N. Computer-assisted LISS plate osteosynthesis of proximal tibia fractures: Feasibility study and first clinical results. Computer Aided Surgery 2005; 10(3): 141-149.    Hofstetter R, Slomczykowski M, Krettek C, Koppen G, Sati M, Nolte LP.: Computer-assisted fluoroscopy-based reduction of femoral fractures and antetorsion correction. Comput Aided Surg. 2000; 5(5): 311-25.    Hofstetter, R., et al., Fluoroscopy-based surgical navigation—concept and clinical applications, computer Aided Radiology and Surgery, Elsevier Scient B. V., pp. 956-960 (1997).    Kelly, The NeuroStation system for image-guided, frameless stereotaxy, neurosurgery, Vol. 37, No. 2, August 1995, pp. 348-350.    Lemieux, L. et al., A patient-to-computed-tomography image registration method based on digitally reconstructed radiographs, Medical Physics, Vol. 21, No. 11, pp. 1749-1760 (1994).
Müller M. E.: Intertrochanteric Osteotomy: Indication, preoperative planning, technique. In: Schatzker J. (ed): The intertrochanteric osteotomy. Springer Verlag, Berlin 1984, p. 25-66.    Pfeiffer S.: Medical simulation systems—navigation and robotics in orthopedic surgery, Institute for Computer Design and Error Tolerance (IRF), University of Karlsruhe (TH), 2004. p. 24.    Reinhardt, et al., Interactive sonar-operated device for stereotactic and open surgery, Proceedings of the Xth Meeting of the World Society for Stereotactic and Functional Neurosurgery, Maebashi, Japan, October 1989, pp. 393-397.    Tang, Thomas S. Y., Calibration and point-based registration of fluoroscopic images, Thesis submitted to Dept. of Computing and Information Science, Queen's University, Kingston, Ontario, Canada (1999).
Besides the most frequently used optical navigation cameras, the recognition of position and orientation of patient and tools or implants can also be achieved by ultrasound-based, electromagnetic, or other detection methods (for example, U.S. Pat. No. 6,503,249). However, the basic principles outlined above are identical.
Regarding the problem outlined above regarding an exact planning for the spatially-correct positioning of implants, now we have the first attempts to merge the implants—analogously to the tools outlined above—virtually by visualization of simplified geometric bodies of these implants with referenced image data (for example intraoperatively produced x-ray images) and thus—in bone areas that are difficult to see—make it more clear for improved alignment of the implant by the operator [Grüzner PA. et al. 2004+2005, Hofstetter et al. 2000]. A decisive problem of this virtual implant position planning is, however, that although the implants, which mostly have a rectangular, plate-like cross section, can be aligned virtually in the computer in the longitudinal direction along the projected bone surfaces of the intraoperatively produced two-dimensional x-ray images, this however, does not ensure that the entire implant support surface comes into contact with the bone surface over the entire surface area. In reality, using this procedure, mostly only a bone contact with insufficient stability can be preplanned, since the implants are mostly planned on a tilt, and thus contact is only obtained along an edge, that is, only along a line, and not, as required, as a full-surface contact.
Therefore it is the task of the invention to provide a technique with which the problems described above can be solved better, so that the implants, to a great extent, have a full-surface contact to the bone after implantation.